July 28, 2008

In a recent speech, former vice president Al Gore implied solar technology is growing at the same rate computer chips are shrinking — basically invoking Moore’s Law without naming the phenomena.

Now I’m all about solar innovation and improvements, but I think Gore’s a bit ahead of himself here. Not unlike a lot of the hyperbole he’s been throwing out there lately. Lots of good, solid and necessary ideas, but tossed into the mix is a pinch of BS and a dash of hucksterism.

“Think about what happened in the computer revolution,” Gore said on NBC’s Meet the Press programme recenty. “We saw cost reductions for silicon computer chips of 50% for every year and a half for the last 40 years,” he said. “We’re now beginning to see the same kind of sharp cost reductions as the demand grows for solar cells — they build new, more efficient facilities to build these solar cells.”

Gore, who has formed a group, The Alliance for Climate Protection, for solar cell creation, was referring to Moore’s Law, which explains the dramatic gains in compute performance. It stems from a 1965 paper written by Intel co-founder Gordon Moore, which found that the number of transistors put on a chip doubles every 18 months.

But does Moore’s Law also apply to the solar energy industry? The short answer is no. As with microprocessor technology, the price and performance of photovoltaic solar electric cell is improving. And Gore can clearly point to price drops of solar cells to make his case. But the efficiency of those solar cells — their ability to convert sunlight into electric energy — is not increasing as rapidly.

Researchers generate hydrogen without the carbon footprint

A greener, less expensive method to produce hydrogen for fuel may eventually be possible with the help of water, solar energy and nanotube diodes that use the entire spectrum of the sun’s energy, according to Penn State researchers.

“Other researchers have developed ways to produce hydrogen with mind-boggling efficiency, but their approaches are very high cost,” says Craig A. Grimes, professor of electrical engineering. “We are working toward something that is cost effective.”

Currently, the steam reforming of natural gas produces most of our hydrogen. As a fuel source, this produces two problems. The process uses natural gas and so does not reduce reliance on fossil fuels; and, because one byproduct is carbon dioxide, the process contributes to the carbon dioxide in the atmosphere, the carbon footprint.

Grimes’ process splits water into its two components, hydrogen and oxygen, and collects the products separately using commonly available titanium and copper. Splitting water for hydrogen production is an old and proven method, but in its conventional form, it requires previously generated electricity. Photolysis of water solar splitting of water has also been explored, but is not a commercial method yet.

Grimes and his team produce hydrogen from solar energy, using two different groups of nanotubes in a photoelectrochemical diode. They report in the July issue of Nano Lettersthat using incident sunlight, “such photocorrosion-stable diodes generate a photocurrent of approximately 0.25 milliampere per centimeter square, at a photoconversion efficiency of 0.30 percent.”

“It seems that nanotube geometry is the best geometry for production of hydrogen from photolysis of water,” says Grimes

In Grimes’ photoelectrochemical diode, one side is a nanotube array of electron donor material – n-type material – titanium dioxide, and the other is a nanotube array that has holes that accept electrons – p-type material – cuprous oxide titanium dioxide mixture. P and n-type materials are common in the semiconductor industry. Grimes has been making n-type nanotube arrays from titanium by sputtering titanium onto a surface, anodizing the titanium with electricity to form titanium dioxide and then annealing the material to form the nanotubes used in other solar applications. He makes the cuprous oxide titanium dioxide nanotube array in the same way and can alter the proportions of each metal.

While titanium dioxide is very absorbing in the ultraviolet portion of the sun’s spectrum, many p-type materials are unstable in sunlight and damaged by ultraviolet light, they photo-corrode. To solve this problem, the researchers made the titanium dioxide side of the diode transparent to visible light by adding iron and exposed this side of the diode to natural sunlight. The titanium dioxide nanotubes soak up the ultraviolet between 300 and 400 nanometers. The light then passes to the copper titanium side of the diode where visible light from 400 to 885 nanometers is used, covering the light spectrum.

The photoelectrochemical diodes function the same way that green leaves do, only not quite as well. They convert the energy from the sun into electrical energy that then breaks up water molecules. The titanium dioxide side of the diode produces oxygen and the copper titanium side produces hydrogen.

Although 0.30 percent efficiency is low, Grimes notes that this is just a first go and that the device can be readily optimized.

“These devices are inexpensive and because they are photo-stable could last for years,” says Grimes. “I believe that efficiencies of 5 to 10 percent are reasonable.”

Grimes is now working with an electroplating method of manufacturing the nanotubes, which will be faster and easier.

Physicists at Penn State and the Raman Research Institute in India have discovered such a mechanism by which information can be recovered from black holes.

They suggest that singularities do not exist in the real world. “Information only appears to be lost because we have been looking at a restricted part of the true quantum-mechanical space-time,” said Madhavan Varadarajan, a professor at the Raman Research Institute. “Once you consider quantum gravity, then space-time becomes much larger and there is room for information to reappear in the distant future on the other side of what was first thought to be the end of space-time.”

Construction has started on a city in Abu Dhabi that will house 50,000 people and 1,500 businesses but use extremely little energy, and what it does use will come from renewable sources.

The city, which is expected to cost $22 billion, will implement an array of technologies, including thin-film solar panels that serve as the facades and roofing materials for buildings, ubiquitous sensors for monitoring energyuse, and driverless vehicles powered by batteries that make cars unnecessary. The city’s founders hope that it will serve as a test bed for a myriad of new technologies being proposed to reduce greenhouse-gas emissions.

Scientists at UC San Diego, UC Santa Barbara and MIT have developed nanometer-sized “nanoworms” that can cruise through the bloodstream without significant interference from the body’s immune defense system and home in on tumors, reminiscent of the science fiction movie, Fantastic Voyage.

The scientists constructed their nanoworms from spherical iron oxide nanoparticles that join together, like segments of an earthworm, to produce tiny gummy worm-like structures about 30 nanometers long. Their iron-oxide composition allows the nanoworms to show up brightly in MRI diagnostic devices.

Using nanoworms, doctors should eventually be able to target and reveal the location of developing tumors that are too small to detect by conventional methods. Carrying payloads targeted to specific features on tumors, these microscopic vehicles could also one day provide the means to more effectively deliver toxic anti-cancer drugs to specific tumors, organs and other sites in the body, in high concentrations without negatively impacting other parts of the body.